“Everyone at ILM said that Empire was the hardest film they ever worked on", says Rinzler. “These are people who have worked on 20, 30 years worth of films.” Part of the biggest headache caused by Empire was Lucas’ idea to make Hoth an ice planet because, in the pre digital age, the matte lines — the fat black lines seen around a model against a bluescreen background —which would normally be hidden against a star field were clear for all to see. “When you see the snow speeder flying against a snow background, nobody would do that. George told me he still has nightmares where he is sitting in dailies and people are shouting out matte lines.”